A = rand(3,4);             
A(:, [1,3]) = [];           
disp('处理后的矩阵 A:');  
disp(A);  

B = rand(5,3);             
B(end-2, :) = [];           
disp('处理后的矩阵 B:');  
disp(B);  

str = "I'm A STUDENT";     
str_lower = lower(str);    
disp('转换小写后的字符串:');  
disp(str_lower);  
str_final = strrep(str_lower, 'student', 'teacher');  
disp('替换后的字符串:');  
disp(str_final);  
